Leinster boss Joe Schmidt is resigned to being without Ireland fly-half Jonathan Sexton for his side's Amlin Challenge Cup quarter-final showdown with London Wasps next month.

Sexton damaged a tendon in his left foot on the eve of Ireland's Six Nations clash with Italy last month and although he was expected to be sidelined for six weeks there were hopes he would make a quicker-than-expected recovery to bolster Leinster's push for domestic honours having also recently shrugged off a hamstring injury.

However, it appears there has been no significant improvement with Schmidt hinting he may be not be back in action until the end of next month which would leave Sexton with precious little time to prove his fitness to British & Irish Lions coach Warren Gatland having long been the favourite to claim the No.10 shirt for Test series against Australia.

"I'm not sure when Jonny will be back available for us...we've been given a five to six week time frame," Schmidt told The Irish Times following his side's recent PRO12 victory over Glasgow. "Whatever we are planning over the next five or six weeks will mean it's probably a little bit too soon for Jonny."

Leinster resume their push for Amlin Challenge Cup glory against Premiership side Wasps at Adams Park on April 5 with Sexton also looking likely to miss his side's crunch league clash with Munster (April 12). The semi-finals of the Challenge Cup on the last weekend of April, should Leinster progress, loom large as Sexton's final chance to prove his fitness with Lions coach Warren Gatland set to name his squad on April 30.

But Schmidt is also confident that Leinster are in safe hands with playmaker Ian Madigan steering his side to the top of the PRO12 with another assured display on Saturday night - providing all of his side's points in their 22-17 victory over their Scottish rivals at the RDS.

"His goal-kicking was first-rate," Schmidt told the Irish Examiner. "He gave us the buffer we needed towards the end with the penalty as well and then his try [and] he made a couple of good line breaks...Defensively also he was working really hard and he got in to make a couple of really big tackles. He slipped off one or two but made some really important ones as well."

With Sexton reportedly bound for Top 14 side Racing Metro, Madigan is set to compete with high-profile signing Jimmy Gopperth who will join the province from Newcastle in the summer. "We have definitely five games left this year. That will give us a decent read. Ian will probably play the bulk of those games as I am not sure when Jonny will be back available again," said Schmidt.

"That will give us a clearer picture because those games are pretty big games for us. Jimmy Gopperth is going to be with us from the start of the season as well and he will be the ideal foil for Ian Madigan. They probably play a bit more similarly than Jonny and Ian do but Jimmy's experience is something Ian will benefit from."